A plurality of switching converters are used as a power supply of typically a disk array apparatus consuming a relatively large current. The switching converters are each used as a direct-current power supply and connected to each other in parallel to supply a voltage of several volts. It is necessary to efficiently control a load borne by each of the switching converters connected in parallel to constitute the power supply. The switching converter serving as such a direct-current power supply is disclosed in Japanese Patent Laid-open Nos. Hei 9-93929/1997 and Hei 9-233816/1997.
FIG. 12 is a diagram showing the configuration of a direct-current power supply based on the prior art. In the figure, reference numerals 2 and 3 denote a DC input and a switching converter (or a DC/DC converter) respectively. Reference numeral 31 denotes a main switch device, reference numeral 32 denotes a transformer and reference numeral 33 denotes a rectifying/smoothing circuit provided on the secondary side of the transformer 32. Reference numerals 34 and 4 denotes a diode and a DC output voltage respectively. Reference numeral 5 denotes a voltage-detecting unit for detecting the DC output voltage 4. Reference numeral 6 denotes a current-detecting unit for detecting an output current and reference numeral 7 denotes a voltage-stabilization control unit. Reference numerals 8 and 9 denote a photocoupler and a switching control unit respectively.
As shown in FIG. 12, the voltage-detecting unit 5, the current-detecting unit 6 and the voltage-stabilization control unit 7 are provided on the output-potential side of the switching converter 3. A control signal generated by the voltage-stabilization control unit 7 is supplied to the switching control unit 9 provided on the input-potential side of the switching converter 3 by way of the photocoupler 8. The switching control unit 9 controls the main switch device 31 by using the control signal supplied through the photocoupler 8 serving as an isolator. The switching control unit 9 controls the main switch device 31 to adjust the DC output voltage 4 of the switching converter 3 and, hence, the load borne thereby.
In the direct-current power-supply apparatus shown in FIG. 12, the propagation speed of the control signal is determined by the propagation speed of the isolation means such as the photocoupler 8. Thus, the control signal cannot be transmitted at a high speed, resulting in a poor response characteristic of the direct-current power-supply apparatus. Furthermore, in order to improve the efficiency of the switching converter 3, the direct-current power-supply apparatus employs a synchronous-rectification circuit and/or a reverse-current-blocking switch to live or not to live a line. In this case, it is necessary to provide a circuit for controlling the synchronous-rectification circuit and/or the reverse-current-blocking switch. Since such a control circuit operates with a reference electric potential supplied by way of a signal-isolating means as a separate electric potential, however, improvement of the response characteristic of the direct-current power-supply apparatus cannot be expected. In addition, since there is also required a multi-function control circuit operating with a reference electric potential supplied as a separate electric potential, reduction of the size and the cost of the direct-current power-supply apparatus cannot be expected either.
A direct-current power-supply apparatus provided by the present invention comprises a switching converter for converting an input direct-current power into another direct-current power, a control circuit and an isolation means. The switching converter has a main switch device for generating a pulse voltage from the direct-current input, a synchronous-rectification circuit on the output side of the switching converter and a reverse-current-blocking switch. On the other hand, the control circuit employed in the direct-current power-supply apparatus comprises a PWM formation unit, a synchronous-rectification control unit and a driving control unit. The PWM formation unit is a unit for driving the main switch device. The synchronous-rectification control unit is a unit for controlling an operation to drive the synchronous-rectification circuit. The driving control unit is a unit for controlling an operation to drive the reverse-current-blocking switch. The control circuit operates by using an electric potential appearing on the output side of the switching converter as a reference electric potential.
The direct-current power-supply apparatus provided by the present invention applies a driving signal to the main switch device through the isolation means. The direct-current power-supply apparatus provided by the present invention is capable of executing control without exchanging the signal for driving the main switch device and a signal isolated between control devices including a switch for synchronous rectification.